Tens of thousands of Czechs have staged one of the country's biggest protests since the fall of communism, marching in Prague against spending cuts, tax rises and corruption, and calling for the end of a centre-right government already close to collapse.

Police estimated between 80,000 and 90,000 workers, students and pensioners marched through the capital on Saturday to rally in Wenceslas Square. Chanting and whistling, the crowd held banners reading "Away with the government" and "Stop thieves".

The demonstration against Prime Minister Petr Necas's government is the third such trade union-led protest in 12 months against austerity measures, and the turnout underlined mounting public frustration after a series of corruption scandals.

"This government is devastating state structures and is demeaning the unprotected with its asocial reforms," Jaroslav Zavadil, the head of the Confederation of Trade Unions, told the crowd.

The Czech Republic's centre-right government says the budget cuts and reforms of pension and health care plans are needed to bring the budget deficit back below 3% of GDP and maintain market reliability.

Necas said in a statement on Saturday that he respects the people's right to express their view, but defended the measures: "As the prime minister, I feel a great responsibility for our country not to fall into a debt trap."

The Czech government's future looks uncertain after several members of Public Affairs, a junior coalition partner, quit last week after its informal chairman, Vit Barta, was convicted of paying bribes.

Unions warned the government they were ready to organise more radical protests, including a general strike, if their demands are not met.

"We'll paralyse the country until the government falls," said Bohumir Dufek, another union leader.

Tomas Frejkovsky, 45, traveled to Prague with 200 people from the eastern city of Ostrava.

"I have to take three jobs to make both ends meet," he said. "Ordinary people only suffer from it all."